Long-distance flights are fraught with the risk of Deep Vein Thrombosis (DVT), a condition wherein blood clots form in deep veins owing to sitting immobile for a long time. Aviation medicine experts say any flight longer than four hours can pose a risk of DVT but the ones longer than 12 hours can be the trickiest.

In DVT, clots form in a deep vein, especially in the pelvis region, thigh or the lower part of the leg. It can occur in other parts of the body too, such as liver vein, retinal vein, intestinal vein, brain vein and kidney vein, among others. The clot may break free from the vein wall and proceed toward lungs, blocking blood supply. This is a potentially fatal condition, called Pulmonary Embolism.

Serious threat
According to the World Thrombosis Day Steering Committee, about one crore such cases are reported every year across the world. In India, 1% population that's past the age of 40 years experiences DVT. About 20% of these patients need hospitalisation.

There is a 50% risk of DVT in the patients undergoing orthopaedic surgery, predominantly in those of hip and knee – while the patients undergoing thoracic or abdominal surgery have a 40% risk. In one in hundred cases, DVT patients develop PE, which is deadly. Reportedly, of all the hospitalised DVT patients in India, half are at high risk.

Dr. Sanjeev Sood, empanelled medical examiner, Directorate General of Civil Aviation:
During long-haul flights, those travelling in economy class in particular sit cramped up and don’t move, which causes slowing of blood circulation. There are other factors too, such as dehydration owing to the cabin's low relative humidity and less than optimum oxygen level, which make one prone to DVT.

Ex-Captain Arun Sahgal, Ethiopian Airlines (also served Indian Air Force as Wing Commander for 22 years and 17 years with Air India):
It is essential for passengers too to take a walk to the restroom whenever possible. Instead of pressing the button for water, they can walk up to the attendant. This helps break the confined posture.

Precautions
Experts highly recommend wearing compression stockings, especially the below-knee stockings, to mitigate the risk of DVT. These stockings can help reduce the risk of swelling in the legs. The design of the stocking is such that it exerts a mild pressure on the ankle and assists the blood to flow at ease. Also called flight socks, the compression stockings come in various sizes and with different levels of compression.

Consult a medical expert before buying these stockings. An unfit stocking can adversely increase the risk of DVT. Flight socks can also be purchased from pharmacies at airports and related retail outlets. In addition to this, wearing comfortable, loose clothes will also help. Do not consume alcohol or sleeping pills, and remember to drink plenty of water.

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Fit to fly?
Before boarding your next flight, consult a family doctor if you have:
- Any DVT-related problems
- Any cardiovascular disease
- An age of 60+
- A hereditary tendency of blood clotting
- Cancer and are undergoing chemotherapy procedures
- Undergone a surgery recently, particularly that of legs or the pelvic region
- Problems related to obesity & pregnancy
- Had any treatment related to hormones